Changes In Dynamic Behavior Research Articles

Direct impact of nonequilibrium aggregates on the structure and morphology of Pdadmac/SDS layers at the air/water interface.

We discuss different nonequilibrium mechanisms by which bulk aggregates directly modify, and can even control, the interfacial structure and morphology of an oppositely charged polyelectrolyte/surfactant (P/S) mixture. Samples are categorized at the air/water interface with respect to the dynamic changes in the bulk phase behavior, the bulk composition, and the sample history using complementary surface-sensitive techniques. First, we show that bulk aggregates can spontaneously interact with the adsorption layer and are retained in it and that this process occurs most readily for positively charged aggregates with an expanded structure. In this case, key nonequilibrium issues of aggregate dissociation and spreading of surface-active material at the interface have a marked influence on the macroscopic interfacial properties. In a second distinct mechanism, aggregates inherently become trapped at the interface during its creation and lateral flocculation occurs. This irreversible process is most pronounced for aggregates with the lowest charge. A third mechanism involves the deposition of aggregates at interfaces due to their transport under gravity. The specificity of this process at an interface depends on its location and is mediated by density effects in the bulk. The prevalence of each mechanism critically depends on a number of different factors, which are outlined systematically here for the first time. This study highlights the sheer complexity by which aggregates can directly impact the interfacial properties of a P/S mixture. Our findings offer scope for understanding seemingly mysterious irreproducible effects which can compromise the performance of formulations in wide-ranging applications from foams to emulsions and lubricants.

Experimental analyses of metal-composite bonded joints: damage identification

Abstract The advent of composite co-cured and co-bonded integrated construction in aircraft structures has lead to the replacement of fastened joints with bonded joints between the skins and the stiffeners. Skin-stiffener debondings could occur due to impact or other operational reasons and it is usually internal failure. Damage identification of bonded components, which are often vital elements in many structures, is crucial for the prevention of failure of the entire structure. Thus, different researchers have investigated vibration-based methods as an alternative technique to be used in the structural health monitoring (SHM) systems. Hence, this work consists of investigating experimentally through the vibration-based method, the dynamic behavior changes in a bonded metal-composite structure by using piezoelectric transducer and accelerometers in order to monitory the damage. The damage is an artificial debonding in the joint, which was simulated by inserting Teflon™ tapes within the joint. In-situ inspection as ensured by accelerometer and piezoelectric transducers (PZT) bonded to the structure. Indeed, with a simple comparison of the frequency response functions is difficult to conclude if there is damage in the structure, unless a large damage is presented. However, by using damage metrics, it is possible to identify the damage with more accuracy. Thus, the experimental results obtained by the accelerometers were compared to the data provided by the smart composite sensors (PZT). Finally, it was discussed the advantages and limitations of the experimental analyses and the identification technique proposal.

Tracking migration during human T cell development.

Specialized microenvironments within the thymus are comprised of unique cell types with distinct roles in directing the development of a diverse, functional, and self-tolerant T cell repertoire. As they differentiate, thymocytes transit through a number of developmental intermediates that are associated with unique localization and migration patterns. For example, during one particular developmental transition, immature thymocytes more than double in speed as they become mature T cells that are among the fastest cells in the body. This transition is associated with dramatic changes in the expression of chemokine receptors and their antagonists, cell adhesion molecules, and cytoskeletal components to direct the maturing thymocyte population from the cortex to medulla. Here we discuss the dynamic changes in behavior that occur throughout thymocyte development, and provide an overview of the cell-intrinsic and extrinsic mechanisms that regulate human thymocyte migration.

Fault Detection Considerations in Silicon Based MEMS Resonators by Observing Changes in Dynamic Behaviour

This study is about fault detection in siliconbased MEMS resonators. The main idea in finding out the failure is to establish a proper relationship between the mechanical structure and its electrical equivalent and prosecuting related measurements. In order to determine the type of defect, the electrical equivalent circuit is referenced considering the parasitic effects. Among various possible faults cracks in the beam and particle adhesion are selected to verify the validity of the approach. Simulations are carried out to study the effect of defects on the resonance frequency and amplitude. Results coincide greatly with those of similar investigations giving motivation for further studies to penetrate deep into the matter, thus not being restricted with defining the trouble, but even locate the failure

Dynamic modeling of behavior change

We consider a conceptual and quantitative modeling approach for investigating dynamic behavior change. While the approach is applicable to behavior change in eating disorders, smoking, substance abuse and other behavioral disorders, here we present our novel dynamical systems modeling approach to understand the processes governing an individual’s behavior in the context of problem drinking. Recent advances in technology have resulted in large intensive longitudinal data sets which are particularly well suited for study within such frameworks. However, the lack of previous work in this area (specifically, on the interand intra-personal factors governing drinking behavior of individuals) renders this a daunting and unique challenge. As a result, issues which are typically routine in mathematical modeling require considerable effort such as the determination of key quantities of interest, and the timescale on which to represent them. We discuss the construction of an initial mathematical model for two starkly distinct individuals and make a case for the potential for such efforts to help in understanding the underlying mechanisms responsible for behavior change in problem drinkers. AMS Subject Classification: 91E10, 34K29, 62G10.

Dynamic behavior of short aramid fiber‐filled elastomer composites

Short fiber reinforcement is a suitable way to improve the tribological properties of elastomers. However, rubbers products are often exposed to highly dynamic mechanical loadings. Hereby it is crucial to study the change in dynamic behavior due to the addition of short fibers. Therefore, these properties were investigated in terms of dynamic mechanical thermal analysis, heat build‐up (HBU), and fatigue crack growth resistance under cyclic loadings for two different rubber compounds. A peroxide cured ethylene–propylene–diene rubber (EPDM) and a sulfur cured natural rubber (NR) compound were chosen and reinforced with two types of short aramid fibers. It was found that the short fibers could contribute to the improvement in the crack growth resistance, HBU, and the dynamic mechanical behavior of the composites depending on the testing conditions. POLYM. ENG. SCI., 54:2958–2964, 2014. © 2014 Society of Plastics Engineers

We must consider dynamic changes in behavior in social networks and conduct manipulations: comment on Pinter-Wollman et al.

We must consider dynamic changes in behavior in social networks and conduct manipulations: comment on Pinter-Wollman et al.

Integrated FLAG based Energy Efficient Routing with Drop Minimization in MANET

The conservation of energy and the improvement in lifetime of the network has been a challenging task in Mobile Ad hoc Networks (MANET) due to their dynamic and un-predictable behavior and topology change. A route selection and packet drop due to limited buffer(queue) size are two important factor that causes energy consumption by handling retransmission of dropped packets. So many energy aware routing and queue management strategies have been introduced individually. By combining energy based routing with queue management, the lifetime of the network can be increased most effectively. This paper proposes integrated maximum energy based routing with prediction of the route failure by energy estimation and Dynamic queue initialization to reduce packet drop. We modified AODV protocol and drop-tail queue. A Simulation has been performed on NS-2 with the parameter packet delivery fraction, Throughput, endto end delay and number of packets. By comparison planned approach with the old one better result has obtained. General Terms Energy based routing, Queue management, Energy consumption.

The Control of Global Brain Dynamics: Opposing Actions of Frontoparietal Control and Default Mode Networks on Attention

Understanding how dynamic changes in brain activity control behavior is a major challenge of cognitive neuroscience. Here, we consider the brain as a complex dynamic system and define two measures of brain dynamics: the synchrony of brain activity, measured by the spatial coherence of the BOLD signal across regions of the brain; and metastability, which we define as the extent to which synchrony varies over time. We investigate the relationship among brain network activity, metastability, and cognitive state in humans, testing the hypothesis that global metastability is "tuned" by network interactions. We study the following two conditions: (1) an attentionally demanding choice reaction time task (CRT); and (2) an unconstrained "rest" state. Functional MRI demonstrated increased synchrony, and decreased metastability was associated with increased activity within the frontoparietal control/dorsal attention network (FPCN/DAN) activity and decreased default mode network (DMN) activity during the CRT compared with rest. Using a computational model of neural dynamics that is constrained by white matter structure to test whether simulated changes in FPCN/DAN and DMN activity produce similar effects, we demonstate that activation of the FPCN/DAN increases global synchrony and decreases metastability. DMN activation had the opposite effects. These results suggest that the balance of activity in the FPCN/DAN and DMN might control global metastability, providing a mechanistic explanation of how attentional state is shifted between an unfocused/exploratory mode characterized by high metastability, and a focused/constrained mode characterized by low metastability.

Novel perspectives on the dialogue between neuronal and artificial systems

Event Abstract Back to Event Novel perspectives on the dialogue between neuronal and artificial systems Michela Chiappalone1*, Marta Bisio1, Valentina Pasquale1 and Jacopo Tessadori1 1 Istituto Italiano di Tecnologia, Neuroscience and Brain Technologies, Italy Behaviors, from simple to most complex, require a two-way interaction with the environment and the contribution of different brain areas depending on the orchestrated activation of neuronal assemblies. The environment itself can be manipulated, and the corresponding changes in dynamic behavior can provide useful information for understanding the neural systems themselves. For the above reasons, researchers have begun to explore the possibility to create new in vitro systems at the interface between neuroscience and robotics, a field known as ‘embodied electrophysiology’. At the same time, these systems can provide excellent test beds for electrical training and modulation of neuronal tissue, thus forming the basis of future adaptive, bi-directional Brain Machine Interfaces and Brain Prostheses. The first-ever in vitro closed-loop system was developed at Northwestern University: it consisted of a lamprey brain-stem bi-directionally connected to a small wheeled robot. Inspired by that pioneering study, we developed a novel bi-directional system involving a ‘reduced brain model’ (i.e. neocortical networks kept alive over Micro Electrode Arrays - MEAs) and an artificial system (e.g. a small real/virtual robot, a neuromorphic device). In vitro neuronal systems can be easily ‘engineered’ and manipulated, either chemically or electrically, in an open or closed loop fashion. The realized software architecture guarantees a bi-directional exchange of information between the natural and the artificial part by means of simple linear coding/decoding schemes. Moreover a similar closed-loop experimental paradigm can be exploited for developing novel concept Brain Prostheses, aimed at restoring lost functions in neuronal systems with different topological complexity. Acknowledgements The research leading to these results has received funding from the European Union's Seventh Framework Programme (ICT-FET FP7/2007-2013, FET Young Explorers scheme) under grant agreement n° 284772 BRAIN BOW (www.brainbowproject.eu). Keywords: closed-loop system, Micro-Electrode Arrays, in vitro, dissociated neuronal culture, Electrical Stimulation Conference: MERIDIAN 30M Workshop, Brixen, Italy, 25 Sep - 25 Sep, 2014. Presentation Type: Oral Presentation Topic: Neuroengineering Citation: Chiappalone M, Bisio M, Pasquale V and Tessadori J (2014). Novel perspectives on the dialogue between neuronal and artificial systems. Front. Neuroeng. Conference Abstract: MERIDIAN 30M Workshop. doi: 10.3389/conf.fneng.2014.11.00001 Copyright: The abstracts in this collection have not been subject to any Frontiers peer review or checks, and are not endorsed by Frontiers. They are made available through the Frontiers publishing platform as a service to conference organizers and presenters. The copyright in the individual abstracts is owned by the author of each abstract or his/her employer unless otherwise stated. Each abstract, as well as the collection of abstracts, are published under a Creative Commons CC-BY 4.0 (attribution) licence (https://creativecommons.org/licenses/by/4.0/) and may thus be reproduced, translated, adapted and be the subject of derivative works provided the authors and Frontiers are attributed. For Frontiers’ terms and conditions please see https://www.frontiersin.org/legal/terms-and-conditions. Received: 06 Nov 2014; Published Online: 06 Nov 2014. * Correspondence: Dr. Michela Chiappalone, Istituto Italiano di Tecnologia, Neuroscience and Brain Technologies, Genova, 16163, Italy, michela.chiappalone@iit.it Login Required This action requires you to be registered with Frontiers and logged in. To register or login click here. Abstract Info Abstract Supplemental Data The Authors in Frontiers Michela Chiappalone Marta Bisio Valentina Pasquale Jacopo Tessadori Google Michela Chiappalone Marta Bisio Valentina Pasquale Jacopo Tessadori Google Scholar Michela Chiappalone Marta Bisio Valentina Pasquale Jacopo Tessadori PubMed Michela Chiappalone Marta Bisio Valentina Pasquale Jacopo Tessadori Related Article in Frontiers Google Scholar PubMed Abstract Close Back to top Javascript is disabled. Please enable Javascript in your browser settings in order to see all the content on this page.

2D12 新生児における聴覚システムの動特性経時変化(OS9-3:臨床バイオメカニクスと医療デバイス(3))

2D12 新生児における聴覚システムの動特性経時変化(OS9-3:臨床バイオメカニクスと医療デバイス(3))

Semiactive Friction Damper for Lightweight Pedestrian Bridges

In many cases, structural damping of lightweight structures is quite low. Therefore, additional damping systems have to be applied. These systems are, in most instances, passive ones. Concerning lightweight structures, live loads become decisive with respect to the eigenfrequencies of the system affected. Resultant changes in dynamic behavior lead to a loss of the optimal adjustment of the passive systems, which is often followed by disturbing vibrations. This in turn leads directly to an impairment of serviceability. Semiactive damping systems can solve these problems by actively reacting to changes of the system. The following article focusses on the development of a semiactive friction damper using piezoelectric stack actuators in order to reduce the vibrations of a large-scale model of a pedestrian bridge.

Changes in dynamical behavior of ionic liquid in silica nano-pores

Dielectric relaxation measurement has been carried out on an ionic liquid (1-butyl-3-methyl imidazolium hexafluorophosphate, [BMIM][PF6]) confined in nano-porous silica matrix. Two dielectric relaxation peaks have been observed in the confined ionic liquid (IL) while there is only one relaxation peak for bulk IL. Confinement results in layering of some IL molecules near the pore wall while other molecules, less affected by pore wall interaction, remain in the central core. The two relaxation peaks are assigned to the different dynamical behaviors of the central core and layered IL molecules.

New Method to Predict the Surface Tension of Complex Synthetic and Biological Polyelectrolyte/Surfactant Mixtures

Although the surface tension of complex mixtures determines the fate of many important natural processes, the property is notoriously difficult to interpret. Here we announce a new method that successfully predicts the surface tension of two synthetic and one biological polyelectrolyte/surfactant mixtures in the phase-separation region after dynamic changes in the bulk phase behavior have reached completion. The approach is based on the nonequilibrium framework of a lack of colloidal stability of bulk complexes in compositions around the charge match point of the oppositely charged components and requires as input parameters only the surface tension isotherm of the pure surfactant and some bulk measurements of the mixtures; no surface measurements of the mixtures are required. The complexity of the problem is reduced to a single empirical equation. This simplification in our understanding of the surface properties of strongly interacting mixtures involving macromolecules can lead to the optimization of applications involving synthetic polymers and biomacromolecules such as DNA at surfaces.

The Characteristic Parameter Estimation of Low Temperature Target Weak Signal Based on VanderPol-Duffing System

The weak signal, which is usually submerged in strong noise, is very difficult to detecte for its amplitude and frequency. The dynamic properties of VanderPol-Duffing are studied in this paper. Such system can go into the chaos under certain parameters. In chaotic state the disturbance of weak periodic signals can make the system dynamic behavior change dramatically. Our research results show that the system is from period doubling state to chaotic state when the amplitude of input signal is changed. And it has a remarkable impact influence on the system dynamic performance when the input frequency is varied. The unknown frequency can be detected through counting the numbers of turning point in phase diagram. The simulation results verified that the presented method is feasible and there are a lot of theory values in the research.

Angular analysis of the cyclic impacting oscillations in a robotic grinding process

In a robotic machining process, a light-weight cutter or grinder is usually held by an articulated robot arm. Material removal is achieved by the rotating cutting tool while the robot end effector ensures that the tool follows a programmed trajectory in order to work on complex curved surfaces or to access hard-to-reach areas. One typical application of such process is maintenance and repair work on hydropower equipment. This paper presents an experimental study of the dynamic characteristics of material removal in robotic grinding, which is unlike conventional grinding due to the lower structural stiffness of the tool-holder robot. The objective of the study is to explore the cyclic nature of this mechanical operation to provide the basis for future development of better process control strategies. Grinding tasks that minimize the number of iterations to converge to the target surface can be better planned based on a good understanding and modeling of the cyclic material removal mechanism. A single degree of freedom dynamic analysis of the process suggests that material removal is performed through high-frequency impacts that mainly last for only a small fraction of the grinding disk rotation period. To detect these discrete cutting events in practice, a grinder is equipped with a rotary encoder. The encoder's signal is acquired through the angular sampling technique. A running cyclic synchronous average is applied to the speed signal to remove its non-cyclic events. The measured instantaneous rotational frequency clearly indicates the impacting nature of the process and captures the transient response excited by these cyclic impacts. The technique also locates the angular positions of cutting impacts in revolution cycles. It is thus possible to draw conclusions about the cyclic nature of dynamic changes in impact-cutting behavior when grinding with a flexible robot. The dynamics of the impacting regime and transient responses to impact-cutting excitations captured synchronously using the angular sampling technique provide feedback that can be used to regulate the material removal process. The experimental results also make it possible to correlate the energy required to remove a chip of metal through impacting with the measured drop in angular speed during grinding.

Studies on thermogravimetric analysis and solvophobic interactions of micellization of Pd (II) complex in non aqueous solvents

The present paper deals with the synthesis and characterization of a Pd (II) metal complex by means of various spectroscopic, thermogravimetric and physicochemical techniques. The Pd metal complex was found to be thermally stable with melting point at 193°C. Thermodynamic decomposition parameters and activation energy were obtained using various methods. The micellization behavior of the complex was examined in different alcohols (n=2–5) and at various temperatures. Self assembly of synthesized metallosurfactant resulted in formation of inverted metallomicelles with cmc in range of 0.7–0.8mM. Thermodynamically micellization process was found to be enthalpy driven. Dynamic redox electrochemical behavior changes from reversible to irreversible process with change of alcohol as solvent for different micellar solution. The size of Pd ‘inverse’ metallomicelles was found to increase with increase in the hydrophobicity of the solvent. Moreover, the study also takes into account the role of metal ion in modifying the properties of a metallosurfactant.

SMOOTH AND NONSMOOTH BIFURCATIONS IN MULTI-STRUCTURE MULTI-OPERATING-MODE HYBRID POWER SYSTEMS

Hybrid renewable power generation systems have been developed rapidly in recent years. Due to the inherent fluctuation of availability of energy from renewable sources, systems that are designed to capture energy from such sources and deliver it in loads have to cope with the difficult challenges of maintaining stability under all possible operating conditions. As a result, the structures and operating modes of such hybrid systems are inherently time-varying. Due to their multiple structures and operating-modes, hybrid systems have rather complex dynamic behavior and the design for stable operation requires thorough consideration of the effects of variation in parameters on the operating modes and corresponding stability statuses. This paper presents a formal system description for such systems and a general procedure for analyzing the change of dynamical behavior under parameter variations (i.e. bifurcation) of this kind of systems. A hybrid power system consisting of dual-input buck converters is taken as an example for illustrating the possible complex behavior. We reveal smooth and nonsmooth bifurcation phenomena in this system. Under certain conditions, nonsmooth bifurcations have been observed and verified with full-circuit simulations. Moreover, a detailed analysis based on an averaged model is performed to identify two specific types of bifurcation and evaluate the stability boundaries of the system.

Traumatic axonal injury in the mouse is accompanied by a dynamic inflammatory response, astroglial reactivity and complex behavioral changes.

BackgroundDiffuse traumatic axonal injury (TAI), a common consequence of traumatic brain injury, is associated with high morbidity and mortality. Inflammatory processes may play an important role in the pathophysiology of TAI. In the central fluid percussion injury (cFPI) TAI model in mice, the neuroinflammatory and astroglial response and behavioral changes are unknown.MethodsTwenty cFPI-injured and nine sham-injured mice were used, and the neuroinflammatory and astroglial response was evaluated by immunohistochemistry at 1, 3 and 7 days post-injury. The multivariate concentric square field test (MCSF) was used to compare complex behavioral changes in mice subjected to cFPI (n = 16) or sham injury (n = 10). Data was analyzed using non-parametric statistics and principal component analysis (MCSF data).ResultsAt all post-injury time points, β-amyloid precursor protein (β-APP) immunoreactivity revealed widespread bilateral axonal injury and IgG immunostaining showed increased blood–brain barrier permeability. Using vimentin and glial fibrillary acidic protein (GFAP) immunohistochemistry, glial cell reactivity was observed in cortical regions and important white matter tracts peaking at three days post-injury. Only vimentin was increased post-injury in the internal capsule and only GFAP in the thalamus. Compared to sham-injured controls, an increased number of activated microglia (MAC-2), infiltrating neutrophils (GR-1) and T-cells (CD3) appearing one day after TAI (P<0.05 for all cell types) was observed in subcortical white matter. In the MCSF, the behavioral patterns including general activity and exploratory behavior differed between cFPI mice and sham-injured controls.ConclusionsTraumatic axonal injury TAI resulted in marked bilateral astroglial and neuroinflammatory responses and complex behavioral changes. The cFPI model in mice appears suitable for the study of injury mechanisms, including neuroinflammation, and the development of treatments targeting TAI.

The effect of transcranial direct current stimulation on the motor suppression in stop-signal task

This study examined whether transcranial direct current stimulation (tDCS) of the primary motor cortex alters the response time in motor suppression using the stop-signal task (SST). Forty healthy subjects were enrolled in this study. The subjects were assigned randomly to either the tDCS condition or sham control condition. All subjects performed a stop-signal task in three consecutive phases: without, during or after the delivery of anodal tDCS on the primary motor cortex (the pre-tDCS motor phase, on-tDCS motor phase, and after-tDCS motor phase). The response times of the stopping process were significantly lower in each SST motor phase during or after tDCS (p < 0.05) and shorter immediately during delivery of the tDCS, whereas there was no change after the delivery of tDCS compared to sham condition. In contrast, the response times of the going process were similar under the two conditions (p > 0.05). No subjects complained of any adverse symptoms or signs. Anodal tDCS enhances voluntary going and stopping of movement in executive control. tDCS appears to be an effective modality to modulate motor suppression and its related dynamic behavioral changes in motor sequential learning.